A multidiscipline group has been established with the purpose of developing a left ventricular to aortic pump which is designed for ultimate clinical use. The pneumatically operated assist pump is placed in the paracorporeal location. Blood is obtained from the left ventricular apex and flows into the pump through a segmented polyurethane cannula. The studies currently being performed monitor the assist pump flow rate, pulmonary artery flow rate, arterial pressure, left ventricular pressure, left atrial pressure, and the electrocardiogram. The pump is operated in counterpulsation fashion which permits ventricular decompression. The synchronization unit has been designed such that the synchronization is automatically changed if the heart rate increases or decreases. Current studies are underway to evaluate the use of a modified sac-type blood pump in long-term calf experiments with particular reference to the prevention of thrombus formation. Crystalline albumin coating of segmented polyurethane will be evaluated. A technique has also been developed to monitor coronary sinus blood flow during various phases of long-term left ventricular bypass and this work will be continued. A ventricular failure model produced by coronary artery ligation with microsphere injection into the coronary vessels will also be undertaken during the current year. BIBLIOGRAPHIC REFERENCES: Rosenberg, G., Pierce, W.S., Brighton, J. A., Phillips, W. M., Landis, D. L., and Lenker, J.: A pressure-measuring system for long-term in vivo pressure measurements. Surgery, 79:456-459, 1976. Pennock, J. L., Pierce, W.S., and Waldhausen, J. A.: Quantitative evaluation of left ventricular bypass in reducing myocardial ischemia. Surgery, 79:523-533, 1976.